Classical philosophy and Darwinian biology are far more compatible than is usually assumed. In fact, looking at either from the standpoint of the other can enrich and deepen our appreciation of both. From a Darwinian point of view, the theories of Plato and Aristotle deserve to be taken very seriously. From the classical point of view, Darwinian biology is much less reductionist than its enemies suppose.

Sunday, March 6, 2016

The Evolution of Fairness

I have been very interested of
late in the logic of justice. Plato’s
Socrates assumed that justice was an idea, which is to say a logically coherent
form. Just as you know that a triangle
has three angles and that the angles add up to 180 degrees, regardless of the
dimensions of the plane figure, if you
understand what a triangle is, so you will know what the right thing to do in
any context if you understand the logically idea of justice.

My field of research involves the
historical dimension of this idea. How
is that the dimension of justice emerged in the evolution of the human soul? That it did emerge is not in doubt. Even if you think that claims of justice are always
or almost always confidence games, you might want to know why they work. What are human beings charmed by the idea of
justice? To put that question in a more
useful form: how did human beings become the kind of creatures that could be so
charmed?

Game theory, paired with
evolutionary psychology, has come a long way toward answering that
question. The ultimatum game presents
justice in a simple, logical dilemma. In
this game, two individuals (the Proposer and the Responder) must come to an agreement
over the division of a benefit. The one
proposes a distribution: 90% me, 10% you, 50/50, etc. The other must accept the distribution, or
neither of them gets anything.

Simple economic theory predicts
that the responder will accept any distribution above 100/0, for something is
better than nothing. However, when the
game is played with real persons, the proposer usually offers considerably more
than the minimum and the responder usually rejects any offer that is not close
to parity. This is evidence that the
human mind is robustly aware of the logic of fairness.

So why does the partner at an
advantage offer more than the minimum and why does the partner at a
disadvantage refuse to accept an unfair distribution at the price of
nothing? It might make perfect sense to
do so if the tables might be turned next time.
If I am generous to the responder now, he may be generous to me when he
gets to be the proposer. If he screws me
now, just wait until next year. I’ll get
that bastard.

That makes sense if proposers and
responders are randomly assigned their roles with each turn. Stéphane Debove, Nicholas Baumard, and
Jean-Baptiste André move this logic one essential step forward in their essay “Evolution
of equal division among unequal partners.”
Find it in Evolution 69-2:
561-569.

Debove et. al. point out that a
random assignment of roles in natural encounters is not plausible. In nature, stronger individuals will find
themselves in the role of proposer again and again, and vice versa. If the stronger individual doesn’t have to
fear that he will end up in the responder role, what incentive does he have to
be generous?

The answer is that the stronger
individual is not competing only with the weaker ones for prizes; he is
competing also with stronger individuals for partners. If weaker partners are readily available, the
cost of choosing any one partner is low.
It is in the advantage of the stronger individual to make as many
partnerships as fast and as often as possible.
The easiest way to close those deals is to be generous.

Our authors calculate that the
generosity of the stronger proposers will decline as the supply of weaker
responders goes down. When fewer deals
are possible, it pays to be choosy. But
even when weaker responders are few, and the cost of choosing is greatest, generosity
will increase over time.

This piece of research is not
based on empirical evidence. It is based
on simple logic. It makes the case that
nice guys finish first, eventually, regardless of the particular
situations. Plato was right. I note that the authors opened with a mention
of Plato and Rousseau.